In summary, I'm trying to undo a potentially un-wise decision a few years back when I purchased a second hand time trial bike. Great condition, beautiful machine, but 9 speed shimano.

I have an 11 speed road bike which is my pride and joy and an old 10 speed shimano Giant, which I'm in the process of taking apart. The group set is in good condition however.

What are my options here. I've always been confused about 9 vs 10 vs 11 speed compatibility. Ideally, having one set of wheels that I could transfer between both road and TT bikes is what I'm chasing.

My questions are:1. Is the 9 speed a problem here?2. If so, can any of the current 9 speed compatible group set remain assuming condition ok, or am I getting rid? 3. Again assuming ok condition, is there any place for a 10 speed shimano road groupset from my old bike going on to the TT bike?

I'm trying to avoid splashing out on a new TT groups if at all possible.

Sincere apologies for my lack of knowledge in this department.Hopefully anyone can help!Gav

Hi Gavin, your plan sounds sensible but it's going to mean either some upgrading of components or swapping out cassettes.

If you want to run different speed groups on a single set of wheels then your only option is to get an 11-speed set of wheels and 9, 10 and 11 speed cassettes. You would then have to swap the cassette over depending on which bike you were riding. The 9 and 10 speed cassettes will need a spacer that should come with the wheels but an LBS will have loads kicking about. This is probably the best option and swapping a cassette takes 5 minutes so it's not really problematic. You'll have to keep on top of cassette and chain wear on the different bikes but it will be fine.

A ten speed road group will work fine on the TT bike but you'll need new shifters. Not that expensive but not really necessary if you go for the swapping cassettes option and you could keep the Giant as a winter bike.

If it were me, I'd go the wheels option and keep all three bikes. If you want to get rid of the 10 speed one I'd sell all the bits and do the wheels option with the 11 speed and 9 speed bikes.